A V I F A U N A OF THE SOUTHWEST I S L A N D S OF P A L A U

ATOLL RESEARCH B U L L E T I N N O * 267

AVIFAUNA OF THE SOUTHWEST I S L A N D S OF PALAU

BY

SEPTEMBER 198 3

-. Sonsorol

*

.

^{Pulo Anna}

M e r i r

F i g u r e 1. M a j o r i s l a n d s o f P a l a u , i n c l u d i n g t h e s i x S o u t h w e s t I s l a n d s .

A V I F A U N A OF THE SOUTHWEST I S L A N D S OF P A L A U

by John Engbr i n g ¹

INTRODUCTION

The P a l a u A r c h i p e l a g o ( 7 " 2 0 ' N , 134' 3 0 ' E) l i e s a t t h e w e s t e r n m o s t edge of t h e P a c i f i c , j u s t n o r t h of t h e e q u a t o r and n e a r l y e q u i d i s t a n t from New Guinea t o t h e s o u t h , t h e P h i l i p p i n e s t o t h e w e s t , and Guam t o t h e n o r t h e a s t ( F i g u r e I ) , A s a p a r t of M i c r o n e s i a , P a l a u became a U n i t e d S t a t e s T r u s t T e r r i t o r y f o l l o w i n g World War 11, The government i s now i n a t r a n s i t i o n a l s t a t e , and i s s h i f t i n g from a trrlst

The Southwest I s l a n d s of P a l a u a r e composed of s i x t i n y i s l a n d s , e a c h l e s s t h a n 2 km2, e x t e n d i n g 600 km s o u t h w e s t of t h e c a p i t a l , Koror.

The i s l a n d s a r e S o n s o r o l and Fanna ( t h e S o n s o r o l I s l a n d s ) , P u l o Anna, M e r i r , T o b i , and Helen. Other p l a c e names f o r t h e i s l a n d s , and a r e a s , a r e l i s t e d i n Bryan ( 1 9 7 1 ) , Tobi and H e l e n , t h e s o u t h e r n m o s t of t h e g r o u p , l i e o n l y 400 km n o r t h of w e s t e r n New Guinea. A l l of t h e i s l a n d s a r e of low e l e v a t i o n , w i t h a s u b s t r a t e of c o r a l l i n e r u b b l e i n t e r s p e r s e d w i t h sandy a r e a s . Most of t h e i s l a n d s h a r b o r minor d e p o s i t s of p h o s p h a t e , much of which was removed b e f o r e World War I1 d u r i n g t h e J a p a n e s e a d m i n i s t r a t i o n ( H u t c h i n s o n 1 9 5 0 ) - The i s l a n d s s u p p o r t r e l a t i v e l y v e r d a n t f o r e s t s , w i t h c o c o n u t ( Cocos n u c i f e r a ) b e i n g t h e dominant s p e c i e s on m o s t , O t h e r t r e e s i n c l u d e A r t o c a r p u s s p p . , F i c u s s p p . , CaLop'nyllmi h o p h j i l l u n , B a r r i n g t o n i a a s i a r i c a , Pandanus s p , , T o u r n e f o r t i a a r g e n t e a , Scaevoba t a c c a d a , Neisosperma ~ o s i t i f o l i a , and E u g e n i a j a v a n i c a , Other t h a n H e l e n , i h i c h h a s a l a r g e e n c i r c l i n g o u t e r r e e f and a n i n n e r l a g o o n , t h e i s l a n d s a r e s u r r o u n d e d by f r i n g i n g r e e f s t h a t g e n e r a l l y e x t e n d 200-600 m from l a n d b e f o r e d r o p p i n g o f f s t e e p l y i n t o o c e a n d e p t h s . These f r i n g i n g r e e f s form r o c k y f l a t s t h a t a r e exposed a t low t i d e s ,

P o l i t i c a l l y , t h e i s l a n d s a r e p a r t of P a l a u , b u t t h e r e s i d e n t s a r e c u l t u r a l l y d i s t i n c t and s p e a k a s e p a r a t e l a n g u a g e . H i s t o r i c a l l y , a l l t h e i s l a n d s e x c e p t H e l e n have been i n h a b i t e d by M i c r o n e s i a n s r e l a t e d t o t h o s e of o t h e r o u t e r i s l a n d s i n t h e Western C a r o l i n e s ( E i l e r s 1935, 1 9 3 6 ) . Though d e n s e l y p o p u l a t e d a t o n e t i m e , o n l y a few f a m i l i e s r e s i d e

1 U.S

.

F i s h and W i l d l i f e S e r v i c e , H o n o l u l u , Hawaii M a n u s c r i p t r e c e i v e d J u l y 1981 -- Eds

.

t h e r e t o d a y . The economy r e m a i n s a t a s u b s i s t e n c e l e v e l , w i t h c o p r a t h e n e a r l y s o l e s o u r c e of income; o t h e r minor t r a d e i t e m s i n c l u d e c o c o n u t s y r u p , s h e l l s , and h a n d i c r a f t s . On H e l e n , s e a cucumbers a r e a l s o c o l l e c t e d , d r i e d , and e x p o r t e d f o r c o n s u m p t i o n i n t h e O r i e n t . C o n t a c t w i t h t h e o u t s i d e w o r l d i s made e v e r y 3-4 months by s h i p from Koror. T h i s " f i e l d t r i p s h i p " s t o p s f o r 1-2 d a y s a t e a c h i s l a n d , p u r c h a s e s c o p r a , d e l i v e r s s t a p l e s , and f u l f i l l s o t h e r n e e d s of t h e r e s i d e n t s .

The a v i f a u n a of t h e S o u t h w e s t I s l a n d s i s u n d e s c r i b e d , a l t h o u g h l a r g e s e a b i r d c o l o n i e s a r e p r e s e n t on Fanna and Helen. From H e l e n , Owen (1977a) r e c o r d e d t h e G r e a t F r i g a t e b i r d ( F r e g a t a m i n o r ) and L e s s e r F r i g a t e b i r d ( F r e g a t a a r i e l ) and Yamashina (1940) r e c o r d e d t h e S o o t y T e r n ( S t e r n a F u s c a t a ) and C r e s t e d T e r n ( T h a l a s s e u s b e r g i i ) . Two u n p u b l i s h e d r e p o r t s , a c h e c k l i s t (Owen 1977b) and a f i e l d g u i d e

(Engbring l 9 8 l ) , g i v e d i s t r i b u t i o n and r e l a t i v e abundance o f S o u t h w e s t I s l a n d s e a b i r d s . O u t s i d e of t h e s e r e f e r e n c e s l i t t l e e l s e i s a v a i l a b l e on t h e b i r d s of t h e r e g i o n .

The f o l l o w i n g r e p o r t i s based on two t r i p s I made t o t h e i s l a n d s w h i l e working i n Palau a s a S m i t h s o n i a n - P e a c e Corps V o l u n t e e r . One

t r i p was i n t h e f a l l from 9-20 November 1977, and one was i n t h e s p r i n g from 18-26 May 1979 ( " s p r i n g " and " f a l l " i n t h i s r e p o r t r e f e r t o s e a s o n s of t h e N o r t h e r n H e m i s p h e r e ) , During e a c h of t h e s e t r i p s t h e s h i p g e n e r a l l y s p e n t 1-2 d a y s a t e a c h i s l a n d , and I s p e n t s e v e r a l h o u r s p e r day on s h o r e making g e n e r a l o b s e r v a t i o n s . S e a b i r d s were a l s o f r e q u e n t l y r e c o r d e d from t h e s h i p a s i t w a i t e d a few hundred m e t e r s from t h e o u t e r edge of t h e r e e f . I s p e n t a t o t a l of 6 d a y l i g h t h o u r s on Fanna, 14 on S o n s o r o l , 15 on P u l o Anna, 8 on M e r i r , 26 on T o b i , and 19 on Helen. O f f s h o r e ( w i t h i n s i g h t of l a n d ) I s p e n t 6 d a y l i g h t h o u r s a t Fanna, 22 a t S o n s o r o l , 8 a t P u l o Anna, 6 a t M e r i r , 16 a t T o b i , and 10 a t H e l e n , A t Helen I s t a y e d o n e n i g h t on s h o r e , when L was a b l e t o o b s e r v e t h e l a r g e number of b i r d s r e t u r n i n g t o r o o s t a t d u s k . Whenever p o s s i b l e , I q u e s t i o n e d t h e l o c a l r e s i d e n t s r e g a r d i n g a v i f a u n a ,

A d d i t i o n a l i n f o r m a t i o n was c o n t r i b u t e d by Warren King, Dennis P u l e s t o n , and Thomas R i t c h i e , who s p e n t 18 and 19 O c t o b e r 1 9 7 9 on Helen and M e r i r w h i l e t r a v e l i n g on t h e M.S. L i n d b l a d E x p l o r e r ; by Greg B r i g h t , who v i s i t e d t h e r e g i o n from 24 November t o 2 December

1978; and by Robert Owen, who s p e n t 30 y e a r s i n P a l a u and v i s i t e d t h e Southwest I s l a n d s on s e v e r a l o c c a s i o n s .

THE ISLANDS S o n s o r o l I s l a n d s ; 5 " 2 0 ' N , 1 3 2 " 1 3 ' E

Because of t h e i r p r o x i m i t y , two i s l a n d s a r e i n c l u d e d i n t h i s group, S o n s o r o l (136 h a ) , which h a s a b o u t 25 r e s i d e n t s , and Fanna (54

h a ) , a n u n i n h a b i t e d i s l a n d l o c a t e d 2 km n o r t h of S o n s o r o l . R e s i d e n t s of S o n s o r o l r e g a r d Fanna a s a r e s e r v e , b u t make o c c a s i o n a l f o r a g i n g e x p e d i t i o n s by dugout c a n o e t o Fanna f o r f i s h , c o c o n u t c r a b s , a n d b i r d s . Both i s l a n d s a r e c o v e r e d by a f o r e s t of t a l l t r e e s w i t h a r e l a t i v e l y well-formed canopy and a m o d e r a t e l y d e n s e u n d e r s t o r y . S e v e r a l huge, s t a t e l y F i c u s and A r t o c a r p u s grow on Fanna.

Fanna h a r b o r s s p e c t a c u l a r s e a b i r d c o l o n i e s . The B l a c k Noddy ( Anous m i n u t u s ) and Red-footed Booby ( S u l a s u l a ) n e s t i n immense

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numbers. Although l e s s p l e n t i f u l , White T e r n s ( G y g i s a l b a ) a r e a l s o a b u n d a n t . I n P a l a u , Fanna i s t h e o n l y known n e s t i n g s i t e f o r G r e a t F r i g a t e b i r d s , and p o s s i b l y L e s s e r F r i g a t e b i r d s a s w e l l . Also r e s i d e n t a r e t h e Brown Noddy (Anous s t o l i d u s ) , and a few Brown B o o b i e s ( S u l a l e u c o g a s t e r ) . Only f o u r s e a b i r d s a r e known t o r e s i d e on S o n s o r o l , none i n p r o f u s e numbers. I n o r d e r of abundance t h e s e a r e t h e Brown Noddy, t h e White T e r n , t h e B l a c k Noddy, and t h e W h i t e - t a i l e d T r o p i c b i r d

( Phaethon l e p t u r u s )

.

F r u i t b a t s ( P t e r o p u s SJ.) a r e c o n s p i c u o u s a r b o r e a l d e n i z e n s on b o t h S o n s o r o l and Fanna, b u t a r e n o t s e e n on t h e o t h e r Southwest I s l a n d s .

Pulo Anna; 4 " 4 0 ' N , 131' 58' E

Pulo Anna ( 5 0 h a ) i s c o v e r e d by l a r g e t r e e s , w i t h a r e l a t i v e l y open u n d e r s t o r y . A s h a l l o w , o p e n , b r a c k i s h swamp, a p p r o x i m a t e l y 200 by 200 m , i s l o c a t e d i n t h e c e n t e r of t h e i s l a n d , The swamp i s l i t t e r e d w i t h d e c a y i n g l o g s , r e m n a n t s of mangrove t r e e s t h a t were c l e a r e d by U.S. m i l i t a r y f o r c e s a f t e r World War I1 d u r i n g a m o s q u i t o c o n t r o l program. Water l e v e l f l u c t u a t e s w i t h t h e t i d e s , though t h e r e i s no above-ground c o n n e c t i o n w i t h t h e o c e a n . A p p r o x i m a t e l y 20 o r f e w e r p e o p l e l i v e on t h e i s l a n d .

R e s i d e n t s e a b i r d s i n c l u d e a n abundance of Brown Noddies and White T e r n s , and l e s s e r numbers of W h i t e - t a i l e d T r o p i c b i r d s and B l a c k N o d d i m . G r e a t F r i g a t e b i r d s c o n n o n l y s o a r above t h e i s l a n d , bu"r.rs n o t known t o n e s t on Pulo Anna, M i g r a t o r y s h o r e b i r d s r e g u l a r l y u s e t h e swamp, which p r o v i d e s an e x c e l l e n t r e s t i n g and f e e d i n g a r e a d e s p i t e i t s l i m i t e d s i z e ,

M e r i r (90 h a ) i s m o d e r a t e l y e l o n g a t e d , j u s t o v e r 2 km from t h e n o r t h e r n t o s o u t h e r n t i p . A typhoon i n t h e m i d - 1 9 6 0 5 d e s t r o y e d much of t h e v e g e t a t i o n , and a t h i c k g r o w t h of medium-sized t r e e s h a s s i n c e grown. Numerous l a r g e , dead t r e e s s t i l l e x t e n d above t h e p o s t - t y p h o o n canopy. A s h a l l o w , h e a v i l y overgrown swamp i s p r e s e n t on t h e s o u t h e r n , i n t e r i o r p o r t i o n of t h e i s l a n d , b u t b e c a u s e i t i s overgrown by s h r u b s , few s h o r e b i r d s u t i l i z e i t . M e r i r i s r i d d l e d w i t h m o s q u i t o s , a n d t h i s , a l o n g w i t h t h e d e n s e u n d e r s t o r y , makes t h e i n t e r i o r g e n e r a l l y i n h o s p i t a b l e . In r e c e n t y e a r s o n l y o n e f a m i l y of f e w e r t h a n t e n p e o p l e h a s r e s i d e d on t h e i s l a n d .

Brown Noddies a r e t h e most a b u n d a n t s p e c i e s o n t h e i s l a n d , w i t h l e s s e r numbers of White T e r n s a n d W h i t e - t a i l e d T r o p i c b i r d s . King

et

a l . (1980) r e c o r d e d Black Noddies i n m o d e r a t e numbers i n 1979.

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F r i g a t e b i r d s , m o s t l y Great b u t a few L e s s e r , r e g u l a r l y s o a r above and r o o s t on t h e i s l a n d , b u t a r e n o t known t o n e s t .

Tobi;

With a b o u t 70 p e o p l e , Tobi ( 6 0 h a ) i s t h e most h e a v i l y p o p u l a t e d of a l l t h e Southwest I s l a n d s . Much of t h e t r i a n g u l a r i s l a n d i s c o v e r e d w i t h t a l l c o c o n u t g r o v e s t h a t a r e r e l a t i v e l y w e l l manicured and h a v e open u n d e r s t o r i e s . A s h a l l o w , c e n t r a l l y l o c a t e d swamp, which i s p a r t l y p l a n t e d w i t h t a r o ( C o l o c a s i a e s c u l e n t a ) , i s l a r g e l y t h e r e s u l t of pre-war p h o s p h a t e mining by t h e J a p a n e s e . The s m a l l amount o f open w a t e r p r o v i d e s good but l i m i t e d h a b i t a t f o r m i g r a t o r y s h o r e b i r d s .

S c a t t e r e d t h r o u g h o u t t h e swamp a r e a a r e l a r g e e a r t h e n mounds, a l s o t h e r e s u l t of mining a c t i v i t i e s , The l i m i t e d amount of n a t i v e f o r e s t on t h e i s l a n d c o n t a i n s s e v e r a l m a s s i v e s p e c i m e n s of F i c u s and Calophyllum.

S e a b i r d d e n s i t i e s on T o b i a r e s i m i l a r t o t h o s e on Pulo Anna, w i t h h e a l t h y p o p u l a t i o n s of Brown Noddies and White T e r n s , and many f e w e r W h i t e - t a i l e d T r o p i c b i r d s and B l a c k Noddies, G r e a t F r i g a t e b i s d s a r e commonly s e e n s o a r i n g o v e r h e a d ,

Helen;

U n l i k e t h e o t h e r Southwest I s l a n d s , Helen i s a n a t o l l and c o n s i s t s of a l a r g e r e e f t h a t e n c i r c l e s a n open l a g o o n (100 km2). The o n l y d r y l a n d , which i s a t t h e n o r t h e r n t i p of t h e r e e f , i s low and s m a l l (ap- p r o x i m a t e l y 25 h a ) , and i s m o s t l y s a n d . At low t i d e , c o n s p i c u o u s s a n d s p i t s e x t e n d t o t h e n o r t h and s o u t h of t h e c r e s c e n t shaped i s l a n d . Though t h e i s l a n d was h i s t o r i c a l l y u n i n h a b i t e d , r e s i d e n t s o f T o b i , n e a r l y 75 km away, made o c c a s i o n a l f o r a y s t o H e l e n . When t h i s s t u d y was made, fewer t h a n t e n p e o p l e l i v e d o n H e l e n , b u t t h e p o p u l a t i o n v a r i e s depending on t h e number of ' B ~ i s i t o r s " Prom T o b i o r o t h e r

Southwest I s l a n d s . The v e g e t a t i o n c o n s i s t s a l m o s t e x c l u s i v e l y of l a r g e coconut t r e e s , medium-sized T o u s n e f o r t i a t r e e s , and a few s p a r s e clumps of g r a s s .

ImpressLve numbers of s e a b i r d s r e s i d e on H e l e n , and s e a b i r d d e n s i t y i s g r e a t e r h e r e t h a n on a n y o t h e r Southwest I s l a n d , The s u p e r b q u a l i t y o f Helen a s a n e s t i n g s i t e i s p r o b a b l y d u e t o i t s i s o l a t i o n , i t s b e a c h e s which a r e p r o t e c t e d from l a r g e waves by t h e o u t e r r e e f , a n d i t s l a g o o n which s u p p l i e s a n a b u n d a n t food s u p p l y . T h e r e a r e s i z a b l e c o l o n i e s of C r e s t e d T e r n s , Black Noddies, S o o t y T e r n s , a n d Red-footed B o o b i e s , and moderate numbers o f Brown B o o b i e s and Black-naped T e r n s ( S t e r n a s u m a t r a n a ) . White T e r n s ~ e c e n t l y began n e s t i n g o n Helen i n s m a l l numbers. Both G r e a t a n d L e s s e r F r i g a t e b i r d s commonly s o a r n e a r t h e i s l a n d and r o o s t i n t h e t a l l c o c o n u t t r e e s . N e i t h e r s p e c i e s is t h o u g h t t o n e s t r e g u l a r l y on H e l e n , b u t a male L e s s e r F r i g a t e b i r d was r e c o r d e d on a n e s t i n 1969 (Owen 1 9 7 7 ) .

A V I FAUNA

Forty-seven s p e c i e s of b i r d s h a v e been r e c o r d e d from t h e S o u t h w e s t I s l a n d s ( T a b l e I ) , of which 14 a r e r e s i d e n t and 3 3 a r e m i g r a n t o r v a g r a n t . Four a d d i t i o n a l g e n e r a h a v e been r e c o r d e d t h a t a r e n o t

i d e n t i f i e d t o s p e c i e s ( T a b l e 1 ) . Out o f t h e 14 r e s i d e n t s p e c i e s , 11 a r e s e a b i r d s and t h r e e a r e l a n d b i r d s . The 11 s p e c i e s of r e s i d e n t s e a b i r d s r e p r e s e n t f o u r f a m i l i e s : P h a e t h o n t i d a e (one s p e c i e s ) , S u l i d a e

(two s p e c i e s ) , F r e g a t i d a e (two s p e c i e s ) , and L a r i d a e ( s i x s p e c i e s ) . C o n s p i c u o u s l y a b s e n t i s t h e f a m i l y P r o c e l l a r i i d a e . Most n o n r e s i d e n t s a r e m i g r a t o r y s h o r e b i r d s . S e v e r a l r e c e n t new b i r d r e c o r d s f o r P a l a u ( E n g b r i n g and Owen 1981, King

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e t a l . 1980) were n o n r e s i d e n t s r e c o r d e d from t h e Southwest I s l a n d s . These a r e t h e R e d - t a i l e d T r o p i c b i r d , Masked Booby, Chinese Goshawk, Bush Hen, Brown S h r i k e , and L a n c e o l a t e d Warbler.

N o n r e s i d e n t B i r d s

Though a number of v a g r a n t and m i g r a t o r y s p e c i e s h a v e been r e c o r d e d from t h e Southwest I s l a n d s ( T a b l e I ) , t h e l i s t i s n o d o u b t i n c o m p l e t e . Any of t h e m i g r a t o r y s p e c i e s a l r e a d y r e c o r d e d from t h e P a l a u A r c h i p e l a g o (Engbring 1981, Owen 1977c) a r e l i k e l y t o o c c u r i n t h e Southwest I s l a n d s a s w e l l . The m a j o r i t y of m i g r a n t s a r e s h o r e b i r d s from t h e E a s t e r n E u r a s i a n Region t h a t a r e moving s o u t h d u r i n g t h e b o r e a l w i n t e r ; a few a r e b i r d s from New Guinea o r A u s t r a l i a t h a t a r e t r a v e l i n g n o r t h d u r i n g t h e a u s t r a l w i n t e r ; and a s m a l l number a r e p r o b a b l y e a s t - w e s t m i g r a n t s from S o u t h e a s t A s i a , t h e P h i l i p p i n e s , o r I n d o n e s i a (Baker 1951). The most common s h o r e b i r d s (5-20 r e g u l a r l y s e e n a t any o n e t i m e on e a c h i s l a n d d u r i n g m i g r a t i o n ) i n c l u d e L e s s e r Golden P l o v e r , Ruddy T u r n s t o n e , Whimbrel, and G r a y - t a i l e d T a t t l e r . I m p o r t a n t h a b i t a t t y p e s u t i l i z e d by s h o r e b i r d s i n c l u d e t h e s m a l l i n l a n d swamps on Pulo Anna and T o b i , r e e f f l a t s , and s a n d y b e a c h e s .

U n i d e n t i f i e d S p e c i e s

A number of b i r d s were o b s e r v e d t h a t were n o t p o s i t i v e l y i d e n t i f i e d : S h e a r w a t e r - P u f f i n u s s p . : One a l l d a r k s h e a r w a t e r was s e e n a b o u t 130 km n o r t h of S o n s o r o l on 26 May 1 9 7 9 . I t s s i z e and c o l o r matched t h a t of t h e d a r k p h a s e of t h e Wedge-tailed S h e a r w a t e r , P u f f i n u s g a c i f i c u s , b u t t h e r e a r e s e v e r a l a l l d a r k s h e a r w a t e r s i n t h e P a c i f i c

w i t h which t h e b i r d c o u l d h a v e been c o n f u s e d . T h i s was t h e o n l y P r o c e l l a r i d t h a t I saw i n 18 d a y s a t s e a .

T a t t l e r

-

H e t e r o s c e l u s s p . : T a t t l e r s were r e g u l a r l y o b s e r v e d on most of t h e i s l a n d s . On t h e b a s i s of c a l l , I i d e n t i f i e d G r a y - t a i l e d T a t t l e r s on M e r i r and Tobi. King

--

e t a l . (1980) i d e n t i f i e d G r a y - t a i l e d T a t t l e r s on Helen and M e r i r . U n i d e n t i f i e d T a t t l e r s c o u l d p o s s i b l y be t h e Wandering T a t t l e r , H e t e r o s c e l u s i n c a n u s , a m i g r a n t i n P a l a u which i s less common t h a n t h e G r a y - t a i l e d T a t t l e r .

T a b l e 1. D i s t r i b u t i o n and s t a t u s of Southwest I s l a n d b i r d s . Common and s c i e n t i f i c names f o l l o w t h e American O r n i t h o l o g i s t s ' Union (1982) c h e c k - l i s t whenever p o s s i b l e . O t h e r names a r e from Owen ( 1 9 7 7 ~ ) and King e t a l . (1975).

--

S t a t u s Symbols

R

-

R e s i d e n t ; n e s t s w i t h i n t h e Southwest I s l a n d s and i s g e n e r a l l y p r e s e n t year-round. D i f f e r e n t c l a s s e s o f r e s i d e n t b i r d s a r e i n d i c a t e d w i t h l o w e r c a s e l e t t e r s a s f o l l o w s :

b - B r e e d i n g s p e c i e s on t h e i s l a n d ; n e s t s , e g g s , o r young r e c o r d e d . p

-

P r o b a b l e n e s t e r on t h e i s l a n d , b u t n e s t s , e g g s , o r young n o t

r e c o r d e d .

t

-

T r a n s i e n t ; r e c o r d e d n e a r ( g e n e r a l l y w i t h i n s i g h t o f ) l a n d , b u t i s n o t t h o u g h t t o n e s t on t h e i s l a n d . May o r may n o t r o o s t on t h e i s l a n d ,

M

-

M i g r a n t ; m i g r a t o r y s p e c i e s n o t r e s l d e n t i n t h e S o u t h w e s t I s l a n d s , V

-

V a g r a n t ; a c c i d e n t a l o c c u r r e n c e of a n o r m a l l y non-migratory s p e c i e s .

Abundance Symbols

S

-

S i n g l e i n d i v i d u a l r e c o r d e d on one o r more o c c a s i o n s . U - Uncommon; 2-10 b i r d s r e c o r d e d on a t l e a s t one v i s i t . C - Common; 11-50 b i r d s r e c o r d e d on a t l e a s t o n e v i s i t ,

N - Numerous; 50-1,000 b i r d s r e c o r d e d on a t l e a s t one v i s i t , A - Abundant; o v e r 1 , 0 0 0 b i r d s r e c o r d e d on at l e a s t one v i s i t *

I s l a n d Symbols FA

-

Fanna,

SO

-

S o n s o r o l . PU

-

Pulo Anna.

ME - M e r i r . TO

-

T o b i . HE

-

H e l e n .

T a b l e 1, c o n t i n u e d

S p e c i e s FA

S h e a r w a t e r g e n u s (M) P u f f i n u s s p . W h i t e - t a i l e d

T r o p i c b i r d (R) P h a e t h o n l e p t u r u s R e d - t a i l e d T r o p i c b i r d (M) Phaethon r u b r i c a u d a Masked Booby ( V )

Brown Booby (R) Red-footed Booby ( R ) G r e a t Fr i g a t e b i r d (R) L e s s e r F r i g a t e b i r d ( R ) C a t t l e E g r e t (M)

P a c i f i c Reef Heron (R) L i t t l e E g r e t (M)

Plumed E g r e t (M) C h i n e s e Goshawk (M) Red J u n g l e f o w l (R) Bush Men (V)

B l a c k - b e l l i e d P l o v e r (M) L e s s e r Golden P l o v e r (M) Mongolian P l o v e r (M)

L i t t l e Ringed P l o v e r (M) O r i e n t a l P l o v e r (M) Common Greenshank (M) Wood S a n d p i p e r (M) G r a y - t a i l e d T a t t l e r (M)

S u l a d a c t y l a t r a S u l a l e u c o g a s t e r S u l a s u l a

-- F r e g a e a minor Frega t a a r i e l Bubulcus i b i s E g r e t t a s a c r a E g r e t t a g a r z e t t a 1 E g r e t t a i n t e r m e d i a A c c i p i t e r s o l o e n s i s

P l u v i a l i s squa t a r o l a P l u v i a l i s dominica Charad r i u s mongolus 2 C h a r a d r i u s d u b i u s C h a r a d r i u s v e r e d u s ³ T r i n g a n e b u l a r i a Tr i n g a g l a r e o l a

He t e r o s c e l u s b r e v i p e s

I s l a n d

UP

j*

s t

St*

Ye zt*

5 UP

3

*

Ub

"

>

U U U

*

S

*

U

T a b l e 1, c o n t i n u e d

I s l a n d

S p e c i e s FA

T a t t l e r g e n u s (M) Common S a n d p i p e r (M) L i t t l e Curlew (M) Whimbrel (M)

B l a c k - t a i l e d Godwit (M) B a r - t a i l e d Godwit (M) Ruddy T u r n s t o n e (M) Ruf ous-necked Sf i n t (M)

S t i n t g e n u s (M) Curlew S a n d p i p e r (M) S n i p e g e n u s (M) Common T e r n (M) Black-naped T e r n (R) Sooty T e r n (R) L i t t l e T e r n (Pi) C r e s r e d T e r n (R)

Brown Noddy (R)

B l a c k Noddy ( R ) White T e r n (R) Nicobar Pigeon (V) O r i e n t a l Cuckoo (M) Cuckoo genus (M) Hawk-Owl g e n u s (M)

H e t e r o s c e l u s s p . A c t i t i s h y p o l e u c o s

Numenius minu t u s Numenius phaeopus Limosa l i m o s a Limosa l a p p o n i c a A r e n a r i a i n t e r p r e s C a l i d r i s r u f i c o l l i s 4 C a l i d r i s s p ,

C a l i d r i s f e r r u g i n e a G a l l i n a g o s p ,

S t e r n a h i r u n d o S t e r n a s u m a t r a n a S t e r n a f u s c a t a S t e r n a a l b i f r o n s T h a l a s s e u s b e r g i i

Gygis a l b a

C a l o e n a s n i c o b a r i c a Cuculus s a t u r a t u s Cuculus s p .

Ninox s p .

T a b l e 1, c o n t i n u e d

Is l a n d

S p e c i e s FA

C o l l a r e d K i n g f i s h e r (R) Halcyon c h l o r i s B e e - e a t e r genus (M) Merops sp.

D o l l a r b i r d (M) Eurystomus o r i e n t a l i s

Barn Swallow (M) Hirundo r u s t i c a

Yellow W a g t a i l (M) M o t a c i l l a f l a v a Brown S h r i k e (M) L a n i u s c r i s t a t u s L a n c e o l a t e d W a r b l e r (M) L o c u s t e l l a l a n c e o l a t a Gray-s t r eaked

F l y c a t c h e r (M) Muscicapa

griseistic.ta

a

It i s n o t c e r t a i n w h e t h e r t h e L i t t l e E g r e t can be s e p a r a t e d from t h e Snowy E g r e t (E.

- -

t h u l a ) , which h a s n o t been r e c o r d e d from Palau. I saw two w h i t e e g r e t s wading on r e e f f l a t s a l o n g t h e s h o r e a t T o b i on 15 November 1977. Both were a l i k e , w i t h n a r r o w plumes on t h e n a p e , b l a c k b e a k s , orange-yellow l o r e s , b l a c k l e g s ( w i t h a g r e e n i s h t i n g e ) , and g r e e n i s h - y e l l o w t o e s .

2 The Mongolian P l o v e r i s s i m i l a r t o t h e G r e a t e r Sand P l o v e r (C, l e s c h e n a u l t i i ) , P r i o r t o my v i s i t t o t h e Southwest I s l a n d s

r e g u l a r l y o b s e r v e d b o t h s p e c i e s i n Kosor, P a l a u , a n d c o n s i d e r e d t h e two s e p a r a b l e on t h e b a s i s of s i z e , l e g l e n g t h , and l e g c o l o r , among o t h e r f i e l d t r a i t s ,

3 Some c o n s i d e r t h i s a s two s p e c i e s , - ^{6 ,} v e r e d u s and

-

^C, a s i a t i c u s ,

4

The Rufous-necked S t i n t i s s i m i l a r t o two o t h e r s m a l l C a l i d r i d s , t h e L i t t l e S t i n t (C, m i n u t a ) and t h e Semipalmated S a n d p i p e r ( C . p u s i l l a ) , and would be d T f f i c u l t t o s e p a r a t e from them i n w i n t e r

plEmage.

The i n d i v i d u a l I o b s e r v e d on H e l e n on 22 May 1979 was e n t e r i n g b r e e d i n g plumage, and had a n even wash of r e d d i s h c o l o r on t h e b r e a s t and neck. I used t h i s t r a i t t o s e p a r a t e i t from t h e o t h e r two s p e c i e s , n e i t h e r of which have been r e c o r d e d from PaLau.

*

Recorded by King

--

e t a l . ( 1 9 8 0 ) .

S n i p e

-

, G a l l i n a g o s p . : I f l u s h e d t h r e e s n i p e on T o b i on 1 4 November 1977, and King

- -

e t a l . (1980) o b s e r v e d one o n Helen o n 18 O c t o b e r 1979. None of t h e s e i n d i v i d u a l s were i d e n t i f i e d t o s p e c i e s , though i t i s l i k e l y t h a t o n e o r more were Swinhoe S n i p e , G a l l i n a g o m e g a l a , t h e o n l y s p e c i e s of s n i p e c o l l e c t e d from P a l a u .

S t i n t

-

C a l i d r i s s p . : I o b s e r v e d two s t i n t s i n w i n t e r plumage, o n e on Helen on 1 3 November 1977, a n d one on Tobi on 17 November 1977.

These a p p e a r e d t o be and most l i k e l y were Rufous-necked S t i n t s , C a l i d r i s r u f i c o l l i s . However, t h e y c o u l d n o t be s a f e l y s e p a r a t e d from t h e w i n t e r plumage L i t t l e S t i n t , C a l i d r i s m i n u t a , o r Semipalmated S a n d p i p e r , C a l i d r i s p u s i l l a , n e i t h e r of which h a s been r e c o r d e d from P a l a u .

Hawk-owl

-

Ninox s p . : An u n i d e n t i f i e d , s m a l l brown owl was f i r s t r e p o r t e d from Helen o n 28 November 1978 ( B r i g h t 1978). On

18 O c t o b e r 1979, a n o t h e r owl was o b s e r v e d t h a t was i d e n t i f i e d a s t h e Brown Hawk-Owl, Ninox s c u t u l a t a (King - - e t a l . 1 9 8 0 ) - The owl was most l i k e l y t h e Brown Hawk-Owl, a s i t i s e w i d e s p r e a d s p e c i e s i n S o u t h e a s t Asia t h a t m i g r a t e s t o t h e P h i l i p p i n e s . However, t h e r e a r e s e v e r a l o t h e r Winox s p p , t h a t r e s i d e on n e a r b y i s l a n d s w i t h which t h e Brown Hawk-owl c o u l d c o n c e i v a b l y be c o n f u s e d .

Cuckoo - Cuculus s p . : I o b s e r v e d one cuckoo on T o b i which was e i t h e r t h e O r i e n t a l Cuckoo, Cuculus s a t u r a t u s , o r t h e Common Cuckoo, Cuculus c a n o r i s .

B e e - e a t e r

-

Merops s p . : I o b s e r v e d a f l o c k of e i g h t b e e - e a t e r s on T o b i on 2 1 May 1979. T e n t a t i v e l y t h e s e h a v e been i d e n t i f i e d a s t h e Rainbowbird, Merops o r n a t u s , a n A u s t r a l i a n s p e c i e s . A l l t h e b i r d s were i n immature plumage, however, and f u r t h e r comparison of t h e A u s t r a l i a n s p e c i e s and ;wo p h i l i p p i n e b e e - e a t e r s s h o u l d

be

made.

I n a d d i t i o n t o e h e above u n i d e n t i f i e d b i r d s , B r i g h t (1978) o b s e s v e d a n all. b l a c k b i r d w i t h a Long t a i l on Tobi on 29 November

1978. The i n d i v i d u a l was a t l e a s t 36 cm l o n g , and had d a r k l e g s , b u t a l i g h t e r b i l l , It perched i n a s m a l l t r e e n e a r t h e edge of t h e swamp, The b i r d was p r o b a b l y a male Common Koel, Eudynamys s c o l o p a c e a , Res i d e n t Land B i r d s

P a c i f i c Reef Heron

-

E g r e t t a s a c r a . The r e e f h e r o n i s r e s i d e n t on a l l of t h e Southwest I s l a n d s , and i s c o n s p i c u o u s a s i t f e e d s on r e e f f l a t s a t low t i d e . The p o p u l a t i o n on e a c h i s l a n d p r o b a b l y numbers no more t h a n 15-20 i n d i v i d u a l s . No n e s t s h a v e been r e c o r d e d . Based on

i t s w i d e s p r e a d i n s u l a r d i s t r i b u t i o n one c a n assume t h a t t h e r e e f h e r o n i s a c a p a b l e o v e r s e a s w a n d e r e r , b u t no p a t t e r n s of movement a r e e v i d e n t i n t h e Southwest I s l a n d s . On H e l e n , r e c o r d s i n d i c a t e a v a r i a t i o n i n p o p u l a t i o n s i z e ; one b i r d was r e c o r d e d i n September 1969 (Owen, f i e l d n o t e s ) , e i g h t b i r d s i n November 1977 ( t h i s s t u d y ) , t h r e e b i r d s i n May 1979 ( t h i s s t u d y ) , and e l e v e n b i r d s i n October 1979 (King e t a l . 1980).

T h i s p o p u l a t i o n f l u c t u a t i o n c o u l d be d u e t o i n g r e s s l e g r e s s ,

r e p r o d u c t i o n , o r s i m p l y c o u n t s of v a r y i n g c o m p l e t e n e s s . It i s u n l i k e l y t h a t r e e f h e r o n s a r e o v e r l o o k e d on H e l e n , b u t b i r d s may be r o o s t i n g on d e r e l i c t s h i p s on t h e s u r r o u n d i n g r e e f , and t h u s missed d u r i n g a c o u n t . White and d a r k p h a s e b i r d s a r e r e p r e s e n t e d i n a b o u t e q u a l p r o p o r t i o n s on a l l t h e i s l a n d s .

Red J u n g l e f o w l

-

G a l l u s g a l l u s . Domestic j u n g l e f o w l a r e r e g u l a r l y h e a r d and s e e n on S o n s o r o l , Pulo Anna, M e r i r , and Tobi. The s p e c i e s i s commonly r a i s e d by r e s i d e n t s , and i s l i k e l y t o be found o n any o f t h e Southwest I s l a n d s , p a r t i c u l a r l y n e a r v i l l a g e s . The s p e c i e s was p r o b a b l y i n t r o d u c e d by e a r l y i s l a n d s e t t l e r s . A few b i r d s a r e p r o b a b l y f e r a l , b u t t h i s i s d i f f i c u l t t o d e t e r m i n e . E a r l y r e p o r t s i n d i c a t e t h a t t h e j u n g l e f o w l was v a l u e d more f o r i t s f e a t h e r s , which were used f o r f i s h i n g l u r e s , t h a n f o r i t s f l e s h (Johannes 1981).

C o l l a r e d K i n g f i s h e r

-

Halcyon c h l o r i s , A few, e v e n l y d i s p e r s e d i n d i v i d u a l s o r p a i r s c a n be l o c a t e d on a n y of t h e Southwest I s l a n d s , 'Ehe p o p u l a t i o n

h s

e s t i m a t e d a t 20 o r fewer on e a c h i s l a n d . I assume t h e s p e c i e s i s r e s i d e n t , b u t found no n e s t s . On H e l e n , o n l y one o r two b i r d s have been r e c o r d e d a t any t i m e , and t h e s e a r e p o s s i b l y v a g r a n t s from o t h e r Southwest I s l a n d s , New Guinea, o r I n d o n e s i a ,

R e s i d e n t S e a b i r d s

E s t i m a t e s of t h e s i z e of n e s t i n g c o l o n i e s a r e summarized i n T a b l e 2 , and s p e c i e s a c c o u n t s a r e a s f o l l o w s :

W h i t e - t a i l e d T r o p i c b i r d - Phaethon l e p t u r u s , Although nowhere a b u n d a n t , i n d i v i d u a l s and s m a l l g r o u p s c a n be found commonly on a l l of

t h e S o u t h w e s t I s l a n d s but H e l e n , P o p u l a t i o n s i z e i s e s t i m a t e d a t u n d e r 50 i n d i v i d u a l s a t any one t i m e on e a c h of t h e i s l a n d s of o c c u r r e n c e . The t r o p i c b i r d s s a b s e n c e from Helen can p r o b a b l y be e x p l a i n e d by t h e l i m i t e d amount of f o r e s t , which s e r v e s a s n e s t i n g h a b i t a t , Though T r e c o r d e d no b i r d s from Fanna, t h e s p e c i e s i s p r o b a b l y r e s i d e n t h e r e , B i r d s were found i n equal. numbers i n s p r i n g and f a i l , i n d i c a t i n g n e g l i g i b l e v a r i a t i o n i n n e s t i n g s e a s o n and no d e f i n i t e m i g r a t o r y p a t t e r n , Though no n e s t s have been r e c o r d e d , t h e s p e c i e s presumably n e s t s i n t h e Southwest I s l a n d s , Elsewhere i n MLcronesia, t h e t r o p L c b i r d h a s been found t o n e s t t h r o u g h o u t t h e y e a r ( B r a n d t 19621, a s i s probab'ly t h e c a s e i n t h e Southwest i s l a n d s ,

Red-footed Booby -

--

S u l a s u l a . The Red-footed Booby i s abundant on t h e two i s l a n d s on which i t n e s t s , Fanna and Helen, and s i g h t i n g s a r e p o s s i b l e n e a r any o f t h e o t h e r Southwest I s l a n d s . Boobies g e n e r a l l y spend t h e day f o r a g i n g o v e r t h e open o c e a n , and p o p u l a t i o n e s t i m a t e s a r e b e s t made i n e a r l y morning o r a t d u s k a s t h e b i r d s l e a v e o r r e t u r n t o l a n d . On H e l e n , i t was p o s s i b l e t o spend two e v e n i n g s on t h e i s l a n d and e s t i m a t e numbers a s t h e b i r d s r e t u r n e d t o r o o s t . On Fanna, t h e p o p u l a t i o n e s t i m a t e is d e r i v e d from a c o u n t of a c t i v e n e s t s . The t o t a l a d u l t p o p u l a t i o n ( f l y i n g b i r d s ) i s a r o u n d 5,000 on Fanna and 2,500 on

T a b l e 2. P o p u l a t i o n e s t i m a t e s f o r r e s i d e n t s e a b i r d c o l o n i e s i n t h e Southwest I s l a n d s

Fanna S o n s o r o l Pulo Anna F l e r i r Tobi Helen

W h i t e - t a i l e d T r o p i c b i r d

1

I I I I I

Red-f oo t e d Booby 5,000 2-3,000

Brown Booby

G r e a t F r i g a t e b i r d L e s s e r F r i g a t e b i r d Black-naped Tern

I I

Sooty Tern 8 0 , 0 0 0

C r e s t e d Tern 5-7,000

Brown Noddy Black Noddy

White Tern 1-2,000 200-500 1-2,000 500- 1 , 0 0 0 20-50

Helen. N e a r l y a l l b i r d s ( o v e r 90%) a r e o f t h e w h i t e r a t h e r t h a n d a r k c o l o r p h a s e .

The Red-footed Booby i s a c o l o n i a l n e s t e r , and c o n s t r u c t s n e s t s of l e a v e s , g r a s s and t w i g s . On Fanna, t h e booby n e s t s h i g h i n t r e e s a l o n g t h e p e r i m e t e r of t h e i s l a n d , and t o lesser e x t e n t i n t h e i n t e r i o r . F a v o r i t e n e s t t r e e s a r e T o u r n e f o r t i a a n d A r t o c a r p u s . R e s i d e n t s o f S o n s o r o l s t a t e t h a t t h e booby r o o s t s s o p r o f u s e l y a t t i m e s t h a t n e s t t r e e s a r e i n j u r e d , and i n d e e d , s e v e r a l t r e e s were c o n s p i c u o u s l y d e f o l i a t e d i n May 1979. T h e r e were a t l e a s t t e n d i s t i n c t s i t e s i n May 1979, e a c h w i t h n e a r l y 100 a c t i v e n e s t s . Thus, t h e r e were a b o u t 1 , 0 0 0 a c t i v e n e s t s on t h e i s l a n d . Young w e r e a t a l l s t a g e s of development.

On Fanna, peak n e s t i n g a c t i v i t y o c c u r s d u r i n g s p r i n g months, and t h e r e i s l i t t l e o r no n e s t i n g i n t h e f a l l . A n e s t i n g c y c l e was a p p a r e n t l y b e g i n n i n g i n November 1977, when a d u l t b i r d s were on t h e ground p i c k i n g up t w i g s and s i t t i n g on n e s t s up i n t r e e s . However, I c o u l d s e e no young o r e g g s from below,

On H e l e n , t h e c o l o n y i s s m a l l e r , b u t d e n s i t y i s g r e a t e r , - B i r d s n e s t i n t h e r e l a t i v e l y low T o u r n e f o r t i a t r e e s , and on P rare o c c a s i o n s i n t h e much t a l l e r c o c o n u t t r e e s ( b o t h T o u r n e f o r t i a and c o c o n u t t r e e s a r e u t i l i z e d f o r r o o s t i n g ) , About 265 downy young, a l o n g w i t h a few n e a r l y f l e d g e d b i r d s , were c o u n t e d i n May 1979. I n October 1979, 91 young a t a l l s t a g e s o f development were c o u n t e d (King

- -

e t a l . 1 9 8 0 ) , and i n November 1977, 25 young were found ( t h i s s t u d y ) , The p a t t e r n i n d i c a t e s n e s t i n g t h r o u g h o u t t h e y e a r , w i t h a p r o b a b l e peak i n s p r i n g months.

Brown Booby - S u l a l e u c o g a s t e r , The Brown Booby i s known t o n e s t o n l y on Helen a n d , i n v e r y l i m i t e d numbers, on Fanna. On H e l e n , t h e c o l o n y numbers from 500 t o 1 , 0 0 0 , b u t on Fanna, f e w e r t h a n 25 a r e p r e s e n t . The s p e c i e s c a n p r o b a b l y be s i g h t e d n e a r o r p o s s i b l y r o o s t i n g on any o f t h e o t h e r S o u t h w e s t I s l a n d s .

3n Helen, p a i r s n e s t i n s h a l l o w l i n e d s c r a p e s i n t h e s a n d , o f t e n j u s t above t h e h i g h t i d e l i n e , C o n c e n t r a t i o n s of n e s t i n g b i r d s a r e

l o c a t e d u n d e r T o u r n e f o r t i a t r e e s on t h e n o r t h e r n and s o u t h e r n p o r t i o n s o f t h e i s l a n d , A few young a r e r a i s e d t h r o u g h o u t t h e y e a r , b u t t h e peak n e s t i n g s e a s o n i s i n s p r i n g months. I n November 1977, 1 c o u n t e d

10 downy young and saw n o i n c u b a t i n g a d u l t s . L i k e w i s e , t h e r e was o n l y minor n e s t i n g a c t i v i t y i n November 1978, when o n l y one n e s t was found

( B r i g h t 1978) and i n October 1979, when 11 a c t i v e n e s t s were l o c a t e d (King e t a l . 1980). I n May 1979, t h e peak of t h e presumed n e s t i n g s e a s o n , I c o u n t e d 6 0 downy young of a l l s i z e s , a l o n g w i t h a t l e a s t 20 i n c u b a t i n g a d u l t s . Large numbers of b i r d s r e t u r n e d a t d u s k t o r o o s t on t h e I s l a n d .

R e s i d e n t s of S o n s o r o l informed me of a s m a l l c o l o n y o f f e w e r t h a n 25 b i r d s t h a t r e c e n t l y began n e s t i n g on Fanna. Although I v i s i t e d Fanna i n b o t h f a l l and s p r i n g and o b s e r v e d Brown Boobies i n t h e a r e a , I d i s c o v e r e d no n e s t s . T h i s new c o l o n y may s u c c e e d p r o v i d e d i t i s n o t u n d u l y d i s t u r b e d by humans, and p r o v i d e d t h e r e l a t i v e l y exposed b e a c h e s

p r o v e s u i t a b l e a s n e s t i n g s i t e s . It i s p o s s i b l e t h a t o n l y H e l e n , whose b e a c h e s a r e p r o t e c t e d by a n o u t e r r e e f , i s c a p a b l e of s u s t a i n i n g a s t a b l e c o l o n y of n e s t i n g Brown Boobies.

G r e a t F r i g a t e b i r d

-

F r e g a t a m i n o r , and L e s s e r F r i g a t e b i r d

-

F r e g a t a a r i e l . F r i g a t e b i r d s o c c u r uncommonly b u t w i d e l y o n t h e o c e a n s a r o u n d P a l a u , 'and can c h a r a c t e r i s t i c a l l y be s e e n s o a r i n g above a n y of t h e Southwest I s l a n d s . G r e a t F r i g a t e b i r d s r o o s t on a l l of t h e Southwest I s l a n d s . L e s s e r F r i g a t e b i r d s h a v e been r e c o r d e d from Merir a n d H e l e n , b u t no doubt f r e q u e n t t h e o t h e r Southwest I s l a n d s a s w e l l . D i s c u s s i o n of t h e s e two s p e c i e s i s combined p a r t l y b e c a u s e of t h e i n c o m p l e t e i n f o r m a t i o n r e g a r d i n g r e l a t i v e numbers of e a c h s p e c i e s . Out o f 400 f r i g a t e b i r d s a t Fanna i n May 1979, I i d e n t i f i e d n e a r l y 150

i n d i v i d u a l s , a l l of which were G r e a t F r i g a t e b i r d s . Only a few i n d i v i d u a l s , a l l G r e a t , were i d e n t i f i e d a t Pulo Anna, M e r i r , and Tobi.

Thus, t h e g r e a t m a j o r i t y of f r i g a t e b i r d s on t h e s e , i s l a n d s a p p e a r s t o be G r e a t F r i g a t e b i r d s . A t Helen, I found a p p r o x i m a t e l y e q u a l numbers of t h e two s p e c i e s i n May 1979, a s d i d King - - e t a l , (1980) i n O c t o b e r 1979.

I n May 1969, however, Owen (1977a) found 25 t o 30 G r e a t a n d o v e r 100 L e s s e r F r i g a t e b i r d s on H e l e n .

Although G r e a t F r i g a t e b i r d s r o o s t on a l l t h e Southwest I s l a n d s , o n l y Fanna i s r e p o r t e d t o h a v e a n e s t i n g c o l o n y , R e s i d e n t s informed me t h a t t h e b i r d s n e s t h i g h i n t h e t r e e s i n t h e s p r i n g of t h e y e a r . I n May 1979 when a b o u t 400 f r i g a t e b i r d s were p r e s e n t , I o b s e r v e d b i r d s e n t e r i n g t a l l t r e e s d u r i n g t h e d a y , b u t I c o u l d l o c a t e no n e s t s , O c c a s i o n a l s p o r a d i c n e s t i n g may o c c u r on o t h e r Southwest I s l a n d s a s w e l l . R e s i d e n t s have r e p o r t e d n e s t i n g on M e r i r , and i n May 1969, Owen

(1977a) r e c o r d e d one male L e s s e r F r i g a t e b i r d on a n e s t a t Helen I s l a n d . The f o l l o w i n g number of f r i g a t e b i r d s was r e c o r d e d d u r i n g s e v e r a l t r i p s t o t h e r e g i o n :

May Nov , Nov , 1 % ~ O e t -

1969 197 7 1978 1979 1979

(Owen ( t h i s ( B r i g h t ( t h i s (King e t 1977) r e p o r t ) 1978) r e p o r t ) - a l , b9m)

Pulo Anna

Mer i r 3 4 o v e r 1 0 m o d e r a t e

150 numbers

T o b i 2 6 1

Helen o v e r 300

130

25 m o d e r a t e numbers

The l a r g e s t c o n c e n t r a t i o n s a r e found t h r o u g h o u t t h e y e a r on Fanna and Helen. The number of b i r d s on e a c h i s l a n d v a r i e s , s u g g e s t i n g t h a t b i r d s t r a v e l from one i s l a n d t o a n o t h e r . The d a t a a l s o i n d i c a t e t h a t b i r d s c o n c e n t r a t e t o n e s t a t Fanna d u r i n g t h e s p r i n g months.

F r i g a t e b i r d s a r e h i g h l y m o b i l e , and much of t h e p o p u l a t i o n may o r i g i n a t e from o r move t o a r e a s o u t s i d e P a l a u . For example, L e s s e r F r i g a t e b i r d s t h a t n e s t on t h e L i n e I s l a n d s have been r e c o r d e d i n t h e v i c i n i t y of t h e Southwest I s l a n d s a n d beyond, a d i s t a n c e of o v e r 6 , 0 0 0

km ( S i b l e y and Clapp 196 7 ) .

Black-naped T e r n

-

S t e r n a s u m a t r a n a . T h i s s p e c i e s o c c u r s o n l y on Helen, where t h e p o p u l a t i o n i s 200-500 b i r d s . It r o o s t s and n e s t s on s h i p w r e c k s on t h e - s ; r r o u n d i n g r e e f . In May 1 9 7 9 , t h e s p e c i e s was con- s p i c u o u s , and s m a l l g r o u p s c o u l d be s e e n f o r a g i n g above t h e lagoon o r c i r c l i n g n e a r s h i p w r e c k s . Only a few were s e e n n e a r t h e i s l a n d i t s e l f , e i t h e r r e s t i n g on s a n d s p i t s a t low t i d e o r c i r c l i n g o v e r h e a d . On t h i s same t r i p I v i s i t e d a n abandoned s h i p e a s t of t h e i s l a n d , where a b o u t 50 t e r n s perched on and c i r c l e d t h e s h i p , One c h i c k and a b o u t 20 eggs w e r e found on t h e d e c k , S a b i n o Z a c h a r i a s , a r e s i d e n t of t h e i s l a n d ,

informed me t h a t g r e a t e r numbers of b i r d s r e s i d e d a t t h e o t h e r t h r e e s h i p w r e c k s on t h e r e e f , The n e s t i n g s e a s o n a p p e a r s t o be i n s p r i n g months o n l y . D e s p i t e t h e r e l a t i v e abundance of Black-naped T e r n s i n May 1 9 7 9 and t h e a p p a r e n t l y w e l l e s t a b l i s h e d n e s t i n g p o p u l a t i o n , t h e r e a r e no r e c o r d s of s i g h t i n g s d u r i n g t h e f a l l . The d i s a p p e a r a n c e of t h e p o p u l a t i o n o u t s i d e t h e b r e e d i n g s e a s o n i s p u z z l i n g , s i n c e t h e y a r e r e l a t i v e l y s e d e n t a r y e l s e w h e r e i n t h e P a l a u A r c h i p e l a g o .

Sooty Tern

-

S t e r n a f u s c a t a . H e l e n h a r b o r s t h e o n l y c o l o n y o f Sooty T e r n s i n t h e Southwest I s l a n d s . T h i s h i g h l y p e l a g i c s p e c i e s r e t u r n s t o l a n d o n l y t o n e s t , a n d , d e p e n d i n g on t h e r e p r o d u c t i v e c y c l e , numbers f l u c t u a t e from a few hundred t o t e n s of t h o u s a n d s on Helen.

D e s p i t e t h e o c c a s i o n a l abundance of b i r d s a t H e l e n , s i g h t i n g s of S o o t y T e r n s n e a r t h e o t h e r Southwest I s l a n d s a r e r a r e , During my two t r i p s t h r o u g h t h e r e g i o n , I h e a r d and saw Sooty T e r n s o n l y a t H e l e n .

A t Helen, eggs a r e l o c a t e d i n s h a l l o w s c r a p e s on t h e g r o u n d , usua1l.y w i t h i n t h e i n t e r i o r of t h e i s l a n d w e l l above t h e h i g h t i d e l i n e , The major n e s t i n g c o l o n y i s l o c a t e d i n t h e c e n t r a l and e a s t e r n p o r t i o n of t h e i s l a n d , which i s a r e l a t i v e l y open a r e a i n t e r s p e r s e d w i t h s m a l l g r a s s clumps, This c o l o n y e x t e n d s t o w e l l w i t h i n t h e

i n t e r i o r of t h e i s l a n d d u r i n g a peak n e s t i n g s e a s o n . Another s m a l l c o l o n y , p o s s i b l y a d i s t i n c t p o p u l a t i o n , i s l o c a t e d on t h e beach on t h e s o u t h w e s t s i d e of t h e i s l a n d . B i r d s a p p e a r t o a v o i d n e s t i n g under t h e t r e e s . The n e s t i n g of Sooty T e r n s on Helen a p p e a r s t o f o l l o w no d i s t i n c t a n n u a l c y c l e . On s e v e r a l t r i p s , t h e f o l l o w i n g e s t i m a t e d numbers of n e s t s and young were r e c o r d e d :

Nov

.

^Nov

.

^{May Oct.}

197 7 1978 1979 1979

( t h i s ( B r i g h t ( t h i s (King e t

r e p o r t ) 1978) r e p o r t )

-

a l . 1 9 m )

f i v e n e s t s 500 n e s t s 10 n e a r l y 37,876 e g g s

a n d 1 5 grown and s m a l l

n e a r l y Young c h i c k s a n d

grown young 3 , 0 0 0 n e a r l y

grown young 150 t o 200 no e s t i m a t e 50 a d u l t s 82,000 a d u l t s a d u l t s of a d u l t s

( e a s t s i d e ) ( s o u t h w e s t ( s o u t h w e s t ( e a s t s i d e ) s i d e ) s i d e )

From t h i s l i m i t e d d a t a , i t a p p e a r s t h a t t h e o n l y c o n c e n t r a t i o n oE n e s t i n g b i r d s d u r i n g t h i s 2-year p e r i o d was i n t h e f a l l of 1979. T h i s

i s i n c o n t r a s t t o t h e normal s p r i n g b r e e d i n g peak f o r most s e a b i r d s of t h e r e g i o n . Elsewhere i n M i c r o n e s i a , t h e s p e c i e s seems t o have s e v e r a l d i f f e r e n t n e s t i n g s e a s o n s , b u t t h e s e a r e p o o r l y d e s c r i b e d ( B r a n d t 1 9 6 2 ) .

C r e s t e d Tern

-

T h a l a s s i u s b e r g i i . The C r e s t e d T e r n n e s t s o n l y a t Helen, where i t c a n r e g u l a r l y be o b s e r v e d i n l a r g e numbers r e s t i n g o n s a n d s p i t s o r f o r a g i n g w i t h i n o r n e a r t h e l a g o o n . During t h e n e s t i n g s e a s o n , t h e a d u l t p o p u l a t i o n i s e s t i m a t e d a t a r o u n d 7,000. Uncommon v i s i t s a r e made t o o t h e r Southwest I s l a n d s a s w e l l , and I r e c o r d e d

s m a l l g r o u p s n e a r Pulo Anna, M e r i r , a n d Tobi.

The C r e s t e d Tern e x h i b i t s a d i s t i n c t n e s t i n g s e a s o n , w i t h peak a c t t v i t y i n s p r i n g and l i t t l e o r no n e s t i n g a c t i v i t y d u r i n g t h e r e m a i n d e r of t h e y e a r , The f o l l o w i n g numbers i l l u s t r a t e t h e p a t t e r n :

Nov, Nov ^, May ~ c t ,

197 7 197 8 197 9 1979

( t h i s ( B r i g h t ( t h i s (King e t

r e p o r t ) 1978) r e p o r t ) - a l . 1 9 E )

---

12 c h i c k s No c h i c k s No c h i c k s 10 s m a l l c h i c k s No e g g s No e g g s 3,250 e g g s 20 e g g s b e i n g

i n c u b a t e d i n c u b a t e d 2-3,000 A d u l t s n o t 7,000 a d u l t s 440 a d u l t s a d u l t s e s t i m a t e d

I n May 1979, t h e b i r d s were a t o r n e a r t h e h e i g h t of t h e i r b r e e d i n g c y c l e . The c o l o n y was l o c a t e d on t h e n o r t h e r n t i p of t h e i s l a n d on a l e v e l , o p e n , sandy a r e a j u s t above t h e h i g h t i d e l i n e . S i n g l e e g g s were d e p o s i t e d d i r e c t l y on t h e s a n d w i t h no n e s t b e i n g made. By p a c i n g , I e s t i m a t e d t h e s i z e of t h e c o l o n y a t 425 m 2

,

t h e r e b e i n g a b o u t 240 e g g s i n e v e r y 25 m2 o r a b o u t 4,080 t o t a l eggs. It a p p e a r e d t h a t n e a r l y a f i f t h of t h e s e e g g s were abandoned, and I t h u s e s t i m a t e d a t o t a l of 3,250 a c t i v e n e s t s . According t o King

--

e t a l . (1980) t h i s i s p r o b a b l y t h e l a r g e s t n e s t i n g c o l o n y o f C r e s t e d T e r n s i n M i c r o n e s i a . A s m a l l amount of n e s t i n g o c c u r s o u t s i d e t h e s p r i n g b r e e d i n g s e a s o n . I n O c t o b e r 1979 King

--

e t a l . (1980) n o t e d a s m a l l c o l o n y ( a b o u t 20 e g g s ) on t h e e a s t e r n s i d e of t h e i s l a n d between t h e Sooty T e r n c o l o n y and t h e beach.

Although t h e C r e s t e d T e r n i s f a i r l y s e d e n t a r y i n P a l a u and l a r g e numbers c a n g e n e r a l l y be found r o o s t i n g and f e e d i n g a t Helen t h r o u g h o u t t h e y e a r , t h e y a p p a r e n t l y wander from Helen I s l a n d o u t s i d e of t h e n e s t i n g s e a s o n . King - - e t a l . (1980) o b s e r v e d o n l y 440 r o o s t i n g a d u l t s

i n O c t o b e r 1979, a marked d e c r e a s e from t h e 7 , 0 0 0 o r more t h a t were p r e s e n t i n s p r i n g of t h e same y e a r , During t h e i r a b s e n c e from Helen, t h e b i r d s p o s s i b l y d i s p e r s e t o t h e n o r t h e r n c o a s t of New Guinea,

Brown Noddy

-

Anous s t o l i d u s , The Brown Noddy i s w i d e s p r e a d , and c a n be found on a l l t h e Southwest I s l a n d s e x c e p t H e l e n . On S o n s o r o l , Pulo Anna, and Tobi, Brown Noddies r e s i d e a t a p p r o x i m a t e l y t h e same d e n s i t i e s . On each of t h e s e i s l a n d s , I e s t i m a t e t h e n e s t i n g p o p u l a t i o n t o number i n t h e h i g h hundreds o r low t h o u s a n d s . A t M e r i r , t h e p o p u l a t i o n i s s l i g h t l y l a r g e r , and on Fanna, i t i s s m a l l e r , a t l e a s t d u r i n g s p r i n g months. The s m a l l s i z e of t h e p o p u l a t i o n on Fanna may be d u e i n p a r t t o i n t e r s p e c i e s c o m p e t i t i o n f o r n e s t i n g s i t e s w i t h B l a c k Noddies, which n e s t i n p r o f u s i o n on Fanna i n s p r i n g . The Brown Noddy b r e e d s m o d e r a t e l y t h r o u g h o u t t h e y e a r , w i t h a d e c i d e d peak d u r i n g s p r i n g months. N e s t s a r e p l a c e d i n t r e e s , f r e q u e n t l y i n t h e crown of a c o c o n u t o r pandanus, The b i r d i s r e l a t i v e l y s o l i t a r y i n i t s n e s t i n g h a b i t s , and g e n e r a l l y o n l y o n e n e s t i s p l a c e d i n a t r e e ,

C e r t a i n p o p u l a t i o n s of Brown Noddies a p p a r e n t l y i n d u l g e i n s e a s o n a l m i g r a t i o n s i n t h e Southwest I s l a n d s , though i n t h e main P a l a u A r c h i p e l a g o , numbers a r e s i m i l a r t h r o u g h o u t t h e y e a r , I n November 1977, L r e c o r d e d no Brown Noddies from Pulo Anna o r T o b i , y e t i n May 1979, t h e s p e c i e s was n e s t i n g i n abundance on b o t h i s l a n d s . On M e r i r a n d S o n s o r o l , however, b i r d s were p r e s e n t i n b o t h f a l l and s p r i n g , P o s s i b l y t h e Pulo Anna and T o b i b i r d s m i g r a t e t o S o n s o r o l o r M e r i r d u r i n g t h e f a l l , b u t t h e y may a l s o j o u r n e y t o r e g i o n s o u t s i d e of t h e Southwest I s l a n d s . It was s u g g e s t e d by a r e s i d e n t of T o b i t h a t t h e c o m p l e t e a b s e n c e of n o d d i e s i n November 1977 was t h e r e s u l t of o v e r h a r v e s t i n g t h e b i r d s w i t h a gun, r a t h e r t h a n a n a t u r a l phenomenon.

Black Noddy

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Anous m i n u t u s . A c o l o n i a l and a b u n d a n t n e s t e r on Fanna and H e l e n , t h e s p e c i e s o c c u r s i n much l e s s e r numbers on t h e o t h e r Southwest I s l a n d s . Peak n e s t i n g o c c u r s i n s p r i n g on Fanna, but o n

Helen n e s t i n g a c t i v i t y c o n t i n u e s t h r o u g h o u t t h e y e a r . A t Fanna i n November 1977, t h e s p e c i e s was a b u n d a n t , but I found no n e s t s . I n May

1979, t h e c o l o n y was n e s t i n g p r o f u s e l y around t h e p e r i m e t e r of t h e i s l a n d up t o 100 m i n l a n d . N e s t s , p l a c e d i n b r a n c h c r o t c h e s , were c o n s t r u c t e d of t w i g s , l e a v e s , and o t h e r d e b r i s , and were h e a v i l y caked w i t h excrement. They were p l a c e d a t a l l l e v e l s i n medium-sized t r e e s .

Counts a t t e n random p o i n t s w i t h i n t h e c o l o n y r e v e a l e d a n a v e r a g e of 64 a c t i v e n e s t s w i t h i n a 20 m r a d i u s of e a c h p o i n t . I e s t i m a t e d t h e t o t a l a r e a of t h e c o l o n y a t n e a r l y 20 h a , and t h e t o t a l number o f a c t i v e n e s t s a t 10,000. A t a n y t i m e d u r i n g t h e day a d e n s e c l o u d of s e v e r a l hundred t o s e v e r a l t h o u s a n d b i r d s c o u l d be s e e n f o r a g i n g w i t h i n s i g h t of t h e i s l a n d .

I n c o n t r a s t t o Fanna, t h e c o l o n y on Helen d i d n o t e x h i b i t s u c h marked s e a s o n a l i t y i n n e s t i n g . On a l l t r i p s t h a t I o r o t h e r v i s i t o r s h a v e made t o t h e i s l a n d , a l a r g e number of b i r d s was n e s t i n g r e g a r d l e s s of t h e s e a s o n . On H e l e n , t h e B l a c k Noddy n e s t s n e a r l y e x c l u s i v e l y i n t h e low T o u r n e f o r t i a t r e e s . I n November 1977, I e s t i m a t e d 1 , 7 0 0 a c t i v e n e s t s a t a l l s t a g e s of d e v e l o p m e n t , from eggs t o f u l l y f l e d g e d young,

I n Nay 1979, I r e c o r d e d a b o u t 1 , 0 0 0 n e s t s , King e t a l , ( 1 9 8 0 ) i n

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October 1979, r e c o r d e d r o u g h l y 1,200 n e s t s ,

O u t s i d e of Fanna and H e l e n , t h e r e a r e no l a r g e c o l o n i e s of Black Noddies i n t h e Southwest I s l a n d s . I n November 1979, I saw none a t Pulo Anna, M e r i r , o r T o b i , In May 1979, a v e r y few were p r e s e n t a t

S o n s o r o l , Pulo Anna, and T o b i , b u t i n a l l c a s e s t h e y were v a s t l y outnumbered by Brown Noddies. King - - e t a l . (1980) o b s e r v e d m o d e r a t e numbers on M e r i r i n October 1979, b u t t h e y were outnumbered by Brown Noddies 20 o r 30 t o o n e . Presumably a few b i r d s n e s t on o t h e r

Southwest I s l a n d s , a l t h o u g h i t r e m a i n s t o be documented. From t h e l i m i t e d i n f o r m a t i o n I h a v e from t h e Southwest I s l a n d s , I d e t e c t e d no major movement p a t t e r n s .

Wherever Black Noddies a r e abundant t h e r e were no o r few Brown Noddies, and s u p e r f i c i a l l y i t a p p e a r s t h a t some form of i n t e r s p e c i f i c c o m p e t i t i o n e x i s t s , However, I f e e l t h a t more i s i n v o l v e d t h a n mutual e x c l u s i o n due t o c o m p e t i t i o n f o r f o o d , n e s t s i t e s , o r o t h e r h a b i t a t p a r a m e t e r s , A p o s s i b l e p a r t i a l e x p l a n a t i o n i s t h e i n f l u e n c e of man on t h e two s p e c i e s of n o d d i e s , The Black Noddy may be s u s c e p t i b l e t o d i s r u p t i o n by humans, a s t h e y a r e a b u n d a n t on t h e t r a d i t i o n a l l y u n i n h a b i t e d i s l a n d s of Fanna and Helen. The Brown Noddy, however, may be more t o l e r a n t of human d i s r u p t i o n , and h a s p e r s i s t e d on i s l a n d s i n h a b i t e d by man.

White Tern - Gygis a l b a . The White Tern i s common t o a b u n d a n t on a l l t h e Southwest I s l a n d s e x c e p t H e l e n , where a r e c e n t l y e s t a b l i s h e d c o l o n y of under 50 b i r d s r e s i d e s . The l a r g e s t c o n c e n t r a t i o n i s o n Fanna, where s e v e r a l thousand b i r d s n e s t . L e s s e r numbers, i n t h e h u n d r e d s o r low t h o u s a n d s , a r e found i n t h e f o r e s t s of S o n s o r o l , P u l o Anna, Mer i r

,

and Tobi

.

U n l i k e most o t h e r s e a b i r d s , t h e White T e r n i s n o t s t r o n g l y a v e r s e t o humans, and f r e q u e n t l y r e s i d e s w i t h i n o r n e a r v i l l a g e s . I n d i v i d u a l s o r p a i r s f o r a g e f a r o u t o v e r t h e o c e a n , and a r e u s u a l l y n o t s e e n f e e d i n g n e a r l a n d . B i r d s do n o t r e t u r n n i g h t l y t o r o o s t , a s i n d i v i d u a l s and s m a l l g r o u p s c a n o c c a s i o n a l l y be s e e n o r h e a r d f l y i n g o v e r w a t e r a f t e r d a r k . B i r d s r o o s t and n e s t i n t r e e s , u s u a l l y h i g h i n l a r g e s p r e a d i n g trees such a s F i c u s , Calophyllum, o r A r t o c a r p u s . When o v e r l a n d , b i r d s a r e r a u c o u s and c o n s p i c u o u s , e s p e c i a l l y d u r i n g morning h o u r s .

The White Tern n e s t s t h r o u g h o u t t h e y e a r i n M i c r o n e s i a ( B a k e r l 9 5 l ) , and presumably d o e s s o w i t h i n t h e Southwest I s l a n d s as w e l l . Though t h e t e r n i s n o t a h i g h l y c o l o n i a l n e s t e r , s e v e r a l p a i r s u s u a l l y occupy t h e l a r g e r , more d e s i r a b l e t r e e s . A peak i n n e s t i n g a c t i v i t y may o c c u r i n s p r i n g . On Fanna, Pulo Anna, and T o b i i n May 1979, numerous b i r d s r e p e a t e d l y l a n d e d a n d l i n g e r e d i n t h e f o l i a g e of t h e u p p e r canopy, and were n o i s y and a c t i v e a s i f d e f e n d i n g t e r r i t o r i e s . B i r d s were e v e n l y d i s t r i b u t e d t h r o u g h o u t t h e f o r e s t e x c e p t o n Fanna, where t h e c o l o n y of White T e r n s d i d n o t o v e r l a p w i t h t h e d e n s e and e x t e n s i v e c o l o n y of Black Noddies, Though I c o u l d n o t l o c a t e e g g s o r young, a few i n d i v i d u a l s perched on b r a n c h e s and a p p e a r e d t o be i n c u b a t i n g . A n e s t i n g c y c l e had a p p a r e n t l y begun o r was j u s t b e g i n n i n g . I n November 1977, White T e r n s on t h e s e i s l a n d s were d e c i d e d l y l e s s a c t i v e . Though a peak i n n e s t i n g may o c c u r i n s p r i n g , n e s t i n g a c t i v i t y h a s been r e c o r d e d i n o t h e r months a s w e l l , I n November 1977 on S o n s o r o l , I n o t e d White T e r n s c a r r y i n g s m a l l f i s h , p o s s i b l y f o r f e e d i n g young. In O c t o b e r 1979, a n i n c u b a t i n g b i r d w a s o b s e r v e d on Helen (King e t a l . 1980)

_-- .

The s m a l l c o l o n y of White T e r n s on Helen became e s t a b l i s h e d i n 1978. I n November 1977, no White T e r n s n e s t e d o r r o o s t e d on Helen. A y e a r l a t e r , B r i g h t (1978) found a t l e a s t 20 t e r n s on t h e i s l a n d , and n e s t i n g was r e p o r t e d by r e s i d e n t s . The c o l o n y h a s remained on t h e i s l a n d a t l e a s t t h r o u g h t h e f a l l of 1979, a s 1 found b i r d s i n Nay 1979, and King - - e t a l e (1980) found a few i n October of t h e same y e a r ,

Though p e r h a p s d e p a u p e r a t e from a worldwide p e r s p e c t i v e , s p e c i e s d i v e r s i t y of s e a b i r d s i n t h e S o u t h w e s t I s l a n d s i s comparable t o o t h e r M i c r o n e s i a n i s l a n d g r o u p s : t h e r e a r e e l e v e n r e s i d e n t s e a b i r d s i n t h e

Southwest I s l a n d s , a b o u t n i n e i n Yap, t e n i n t h e M a r i a n a s , n i n e i n T r u k , t e n i n Ponape, s i x t e e n i n t h e M a r s h a l l s , and t e n i n t h e G i l b e r t s

( F i s h e r 1950, Baker 1951, B r a n d t 1962, Amerson 1969, p e r s . o b s e r v . )

.

The M a r s h a l l I s l a n d s g r o u p h a s a s p e c i e s d i v e r s i t y n o t i c e a b l y g r e a t e r t h a n t h e o t h e r i s l a n d g r o u p s . ,The M a r s h a l l s , however, c o v e r a r e l a t i v e l y v a s t a r e a on t h e n o r t h e a s t e r n edge of M i c r o n e s i a , where components of t h e Hawaiian a v i f a u n a l community a r e r e p r e s e n t e d . The s e a b i r d s of t h e Southwest I s l a n d s a r e a l m o s t e x c l u s i v e l y t r e e - n e s t e r s , s u g g e s t i n g t h a t humans o r o t h e r p r e d a t o r s have e x c l u d e d c e r t a i n